Current. The current time in the order year, month, day, hour, minute, second.
The argument may be an empty vector, producing a 6-element numeric list; or
a string of the letters Y M D h m s and other characters, producing a formatted string.
For example:

Performance Monitor Data Area. Literal (character) vector y
is to hold the fixed-sized
records of “packed” performance monitor data; the old PM data
area (if any) is released. The PM counter
(see 6!:12)is set to 0. If y is an empty vector,
no PM data will be collected.

x is a 2-element vector of
control parameters; 0 0 is
assumed if it is elided.

0{x - what to record
0 - entry and exit
1 - entry and exit and all lines1{x - action on running out of space in y
0 - “wrap”, discard the oldest record
1 - “truncate”, discard the newest record

0 name
1 locale where name is found
2 valence
3 line number(_1 for entry; _2 for exit)
4 space in use (bytes)
5 time (seconds)
6 list of names

Columns 0 and 1 are indices into column 6. Columns 0
to 5 have the same number of (corresponding) elements.

y are indices of
the rows to be unpacked, where 0 is
the oldest row (and _1 is the newest row). All rows are
selected if y is the empty vector.
Rows in the result are
always arranged from oldest to newest and no row is selected
more than once.

6!:12 y

Add y to the PM Counter. PM data is recorded if the PM
counter is greater than 0
and a PM data area is extant. (A non-empty PM data area
must be specified before the PM counter can be changed.)
The result is the value of the PM counter after the operation.

6!:13 y

PM Statistics.
Produces a 6-element vector of the following information:

0 - what to record
0 - entry and exit
1 - entry and exit and all lines
1 - action on insufficient space
0 - wrap
1 - truncate
2 - the maximum number of records
3 - current number of records
4 - whether records have been lost
5 - current value of the PM counter

If no PM data area has been specified the result
is 6$0.The argument y is ignored.